This invention relates to a portable bending brake and more particularly to a bending attachment for a conventional portable bending brake in order to provide additional bending of a previously partially bent sheet material workpiece.
Portable bending brakes are commonly available for bending workpieces of sheet material through a range of angles typically varying from 0.degree. to 120.degree., and generally limited to approximately 110.degree.. Such portable bending brakes are utilized in numerous industries, such as in connection with the installation of aluminum siding onto the exterior of homes. The siding is generally manufactured to be directly installed. In some cases vinyl siding is utilized. However, in almost all situations aluminum trim is utilized to finish off specific areas such as doors and windows, corner edges, moldings, etc. The aluminum sheet material utilized as the trim is generally bent insitu in order to achieve the proper size and fit. The portable bending brake is set up at the job site and the elongated strips of sheet material are bent into the desired shape. For many applications, conventional portable bending brakes are sufficient since the desired bent angle is usually approximately 90.degree..
However, for some applications it is necessary to provide a bend greater than 120.degree. and typically a complete 180.degree. bend is required. These situations arise especially when it is desired to form a hem at one edge of the sheet material workpiece.
Supplemental bending attachments for use with conventional portable bending brakes have been previously suggested in the prior art. One such attachment is described in U.S. Pat. No. 3,913,370. The bending attachment provides for an upstanding stationary clamping member which has a horizontal base portion for mounting in the conventional portable bending brake jaws. A movable workpiece clamping member is pivoted with respect to the stationary clamping member intermediate the upper and lower ends thereof and is movable towards and away from the stationary clamping member. Pivoted to one of the clamping members near its upper end above the pivotal connection between the clamping members, is a movable locking member movable into and out of locking engagement with the upper portion of the other clamping member so as to hold one part of the previously bent workpiece immovably therebetween while performing a supplemental bending operation upon another part of the workpiece by manual upswinging of the bending door of the conventional portable bending brake.
In utilizing the attachment of the aforementioned patent, the attachment is set up apart from the conventional portable bending brake. The locking member is lifted so as to permit pivoting of the movable clamping member from the stationary clamping member. The previously bent workpiece is inserted between the two clamping members and the movable clamping member is then closed onto the workpiece and the movable locking member is placed into locking engagement to provide a tight clamping of the previously bent workpiece in the bending attachment. The entire bending attachment, with the workpiece loaded therein, is then inserted into the jaws of the conventional bending brake and the door of the bending brake is pulled upward to provide the additional bend desired.
Although such supplemental bending attachment has been suggested, its use has been limited because of various drawbacks. Firstly, the bending attachment is a complex device which has numerous movable parts which must be carefully manipulated and accordingly requires special training and skill to operate. Additionally, since the bending attachment is loaded with the workpiece outside of the conventional bending brake, it is cumbersome and quite heavy to take the loaded bending attachment and subsequently insert it into the jaws of the conventional bending brake. In many cases, the length of the sheet material workpiece may be as much as 12'6" and it is quite difficult for one person to insert the loaded bending attachment into the jaws of the conventional bending brake.
An additional limitation of the aforedescribed bending attachment concerns the spacing between the movable and stationary clamping member. Since these two members are locked together by means of a fixed locking member, the spacing between the movable and stationary clamping members is fixed. As a result, should an extremely thin sheet material workpiece be utilized, it may not be suitably clamped when the locking member is closed. On the other hand, if the sheet material workpiece is very thick, the bending attachment may not be able to lock at all and accordingly will not be able to clamp down onto the sheet material workpiece. This problem is further complicated when it is desired to provide a double folded over hem onto a sheet material workpiece. Even assuming that the aforedescribed bending attachment can accommodate a single thickness of sheet material in order to provide a single folded over hem of 180.degree., in order to provide the double folded over hem, the double thickness of the sheet material workpiece must now be inserted. Such double thickness will be too thick to be accommodated by the bending attachment and accordingly it will not be possible to utilize the same bending attachment for both a single and double folded over hem.
It is believed that one reason that the aforedescribed bending attachment is a complex device, is that it had previously been assumed that it was necessary to securely clamp the workpiece in the bending attachment prior to insertion into the jaws of the conventional bending brake. As a result, a complex locking mechanism was provided in order to hopefully get adequate clamping onto the workpiece. It is believed for this reason the aforementioned bending attachment had the various complex parts of the device necessary and required loading of the bending attachment prior to insertion on the portable bending brake.